And silver



' Three MINING-AND SULPHATE PRQUESS COMPANY, OF SAME PLACE.

SIEOIFIGATION forming part of Letters Patent No. 249,419, dated November 8, 1881.

Application filed January 13, 186i. (No specimens) To all whom it may concern n Be it known that 1, WILLIAM L. THOMPSON, of Boston, in the county of Suffolk and State of Massachusetts, have invented certain Improvements in Wet Processes for the Extraction of Gold and Silver, of which the following is a specification. 1

This invention has for its object to provide an improved process for the extraction of precious metals from two subdivisions of the class of ores known as smelting ores in contradistinction to those known as free-milling ores, viz: first, the pyrites division bearing gold and some copper, and second,the silver I end gold bearing division, containing unti l enners i and e. k My invention provides a cheap and eflicient means of extracting the precious metals; and it consists in, first, removing the baser metals 2 by the formation of soluble double sulphides of the base metals and the alkaline metals, and secondly, removing the gold by the fusion of the residuum with an alkaline polysulphide, forming a soluble compound, from which the precious metal may be readily reco ered.

The several steps of the process I will now proceed to describe in detail.

In treating the pyrites ores I p efer to proceed as follows: The ores are firs pulverized 0 and mixed with the sulphide or sulphate of soda, and the mixture is then subjected to a roasting -heat. In practice, with every one hundred parts of an orc containing, say, forty per cent. of the base metals, I would add 5 about eighty parts of the sulphide of soda, or

about one hundred and thirty parts ofjthe sulphate 0t soda but these proportions vary widely with the quality of the ore, and I by no means confine myself to them. A soluble 40 compound is thus formed when the sulphide is used which may be called a double sulphide of sodium and iron, and may be chemically expressed as Na Fe S The formation of this compound may be facilitated if the sulphate 5 is used by the use of a reducing-flame or by adding coal in smallquantitis to said mixture. The soluble compound is next removed by leaching with water. The residue containing the. gold is then fused with a polysulphide of an alkaline metal, such as sodium or potassium,

thus forming in the latter case the aurosulphide of potassium, a soluble compound containing, substantially, all the gold in the ore, andfinally the mess is treated with water to separate the aurosulphide of potassium from the residue in the form of a solution. As for the-proportion of the polysulphide, enough is added to make a ball of the stud when molten--tliat is, the liquid polysulphide makes a mud with the ore. More is used for a light ore than for a dense ore, and one-half the weight of the ore would be a fair proportion in ordinary cases. The process of chemical concentration or chemical separation of the base met:

als from the precious is thus completed, and the oldiu he solution maywbe. rec

any of the wellknown iucthodssuch as by boiling or treatment with acids; v p

In treating the other divisions of ores-win, those containing antimony or arsenic-the ore 7cis pulverized and fused with an alkaline monosulphide, and then treated with water, thereby obtaining the sulphantiinonite or the sulpharseuite of the alkaline metaloiu solution and leaving the ore concentrated! In these cases, 7 5 to every one hundred parts of an ore containin g, say, fifty per cent. of base metals, I would add,in practice, say from sixty to eighty parts of the alkaline monosulphide; but, as before stated ,circumstauces would cause these propor- 8o tions to be widely departed from iumany in stances, and I only state them by way of illustration in ordinary cases, and without in any way limiting myself thereto. From the residue the precious metals may be extracted by any suitable method, as by fusion with apolysulph do'of an alkaline metal, which extracts the gold, and the silver may be extracted as sulphate by well-known processes which oxi dize the sulphide already formed. go

I an! aware ofthe process described by Hendersoi: in his English Patent No. 883 of 1859, and claim nothing that is therein. set forth. Hen erson first forms a regnlus or matte of from hirty to forty per cent. of copper, which 9 5 is the 'usual initial stop. He then fuses the matte'and adds sulphate of sodium to take up the sulphide of gold; then casts in molds and leache's out the aurosulphide of sodium. In my process Iform no matte, but work the row :00

oro with monosulphideof sodium,orits equivar lent, to extract the iron, antimony, and arsenic, and treat, the ore deprived of these elements with d,- polysnlphide of sodium or potassium,- to cause the free gold to form an nurosulphide. Henderson nowhere alludes to the use of polysulphides, and this is an essential feature of my process.

Having thus described my invention, 1 claiml. The process of extracting precious metals from the sulphide ores by removing any rou, antim0ny,0r asenictherein contained by means of and in combination with the monosuiphides of the alkaline metals, as double sulphides, as i set, forth, and afterward removing the gold by fusion with an alkaline polysulphide, and their leaching, substantially as set forth.

2. The prooese'of extracting precious metals from the sulphide ores by removing any iron, antimony, or arsenic therein contained by means of and in combination with the monosulphides of the alkaline metals, as double sulphides, as set forth, and afterward removing the gold by fusion with an alkaline pelysltlphitle and leaching, and finally removing the silver, as sulphatmby oxidation of the sulphide of silver already formed, substantially as set forth.

In testimony whereof I have signed my name to this spemliea-tionfin the presence of two subscribing witnesses, this 11th day of January,

' WILLIAM L; 'THUMPSGN.

Witnesses:

1 BROWN, W. CLiMO. 

